Magnesium ammonium phosphate is a known, naturally occurring mineral that exists in various forms, including the hexahydrate form (MgNH4PO4.6H2O), known as struvite. Struvite is crystalline and can be formed from effluent streams in processes that remove phosphorus from wastewater. Because of its phosphorus content, struvite is useful as a fertilizer.
Struvite produced from wastewater treatment is granular in form and can include associated free water. In general, the smaller the size of the struvite granules, the greater the amount of associated free water. Associated free water imparts weight to the granular struvite, which is disadvantageous with regard to struvite handling, packaging, and transport, and in any event must be removed in order to deliver a dry product to users of struvite. In practice, associated free water can be removed from wet struvite by conventional drying, which normally requires heat treatment. However, drying by heat treatment is energy consumptive and costly.
A need exists for a method for producing dry struvite that does not include heating wet struvite. The present invention seeks to fulfill this need and provides further related advantages.